108 PRACTICAL PARASITOLOGY 



and, pending ultimate preservation, are put into normal saline solu- 

 tion. The bowel-wall is carefully cleared, the contents being taken 

 out in small portions with the spatula. Epithelium and villi are 

 removed with the faeces only when Helminthes are known to lie, or 

 are suspected of lying, between them. Portions of faecal matter, of 

 a size varying from that of a hazel-nut to that of a walnut, are put 

 singly into test-tubes. These are then filled for about a third of their 

 length with normal saline and are well shaken for half to one minute, 

 the orifice being closed with the thumb. About the same quantity of 

 saturated solution of mercuric chloride is then immediately added to 

 the liquid, and the tubes are again shaken for about half a minute. The 

 worms usually become extended, and they may be separated from the 

 substance containing them after several days, or even after several 

 weeks. In the latter case, the material should be transferred intact to 

 bottles, which should then be closed, labelled, and stored for future use. 



To separate the Helminthes, well shake the material and transfer 

 it to glass tubes. Fill the tubes with water to within a few cubic 

 centimetres of the top. Close the orifice with the thumb and shake 

 gently until the preserved material is evenly mixed with the water. 

 If the tubes are now placed upright in a rack, the Helminthes will 

 sink to the bottom and the dirty fluid may be poured off into shallow 

 bowls. The tubes are again filled up with water, inverted, and 

 placed upright in the rack as before, allowing the worms again to fall 

 to the bottom. This process is repeated until the water remains clear. 

 It very often happens, however, that the bowel contents contain 

 substances which, owing to their specific gravity, sink to the bottom 

 as quickly as, or even quicker than, the worms. As soon as the 

 material in suspension has been got rid of, these heavier particles 

 must be removed. The deposit is turned out into shallow glass 

 bowls and thinned with water. The worms are taken out with the 

 spatula or a paint-brush and dropped into alcoholic solution of iodine. 

 They may be arranged according to size and appearance. The thick 

 fluid is poured off the deposit and this, in its turn, is diluted with 

 water. Shallow vessels should be used and the material must be 

 minutely examined, as there are certain small and fragile varieties 

 which remain for a long time in suspension. 



Looss, 1 who was the first to employ this method, says that very 

 small worms sometimes remain between the villi, and that as, after 

 preservation, worms and villi sink to the bottom together, the isolation 

 of the worms becomes a difficult matter. He suggests that the bowel- 

 wall should be cut into pieces, put into glass tubes with some normal 

 saline solution, and the tubes well shaken, when the worms will 



1 Looss, Zool. Anz., xxiv, 1901, p. 302. 



